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| author | Waiman Long <longman@redhat.com> | 2024-07-23 14:10:25 -0400 |
|---|---|---|
| committer | Neeraj Upadhyay <neeraj.upadhyay@kernel.org> | 2024-08-12 23:46:41 +0530 |
| commit | 0aac9daef6763e6efef398faff71f8c593651cce (patch) | |
| tree | eff9795747ece60d52b49dd7199a28f02e071371 /kernel/rcu | |
| parent | 8400291e289ee6b2bf9779ff1c83a291501f017b (diff) | |
| download | linux-stable-0aac9daef6763e6efef398faff71f8c593651cce.tar.gz linux-stable-0aac9daef6763e6efef398faff71f8c593651cce.tar.bz2 linux-stable-0aac9daef6763e6efef398faff71f8c593651cce.zip | |
rcu: Use system_unbound_wq to avoid disturbing isolated CPUs
It was discovered that isolated CPUs could sometimes be disturbed by
kworkers processing kfree_rcu() works causing higher than expected
latency. It is because the RCU core uses "system_wq" which doesn't have
the WQ_UNBOUND flag to handle all its work items. Fix this violation of
latency limits by using "system_unbound_wq" in the RCU core instead.
This will ensure that those work items will not be run on CPUs marked
as isolated.
Beside the WQ_UNBOUND flag, the other major difference between system_wq
and system_unbound_wq is their max_active count. The system_unbound_wq
has a max_active of WQ_MAX_ACTIVE (512) while system_wq's max_active
is WQ_DFL_ACTIVE (256) which is half of WQ_MAX_ACTIVE.
Reported-by: Vratislav Bendel <vbendel@redhat.com>
Closes: https://issues.redhat.com/browse/RHEL-50220
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Tested-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index e641cc681901..494aa9513d0b 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3539,10 +3539,10 @@ schedule_delayed_monitor_work(struct kfree_rcu_cpu *krcp) if (delayed_work_pending(&krcp->monitor_work)) { delay_left = krcp->monitor_work.timer.expires - jiffies; if (delay < delay_left) - mod_delayed_work(system_wq, &krcp->monitor_work, delay); + mod_delayed_work(system_unbound_wq, &krcp->monitor_work, delay); return; } - queue_delayed_work(system_wq, &krcp->monitor_work, delay); + queue_delayed_work(system_unbound_wq, &krcp->monitor_work, delay); } static void @@ -3634,7 +3634,7 @@ static void kfree_rcu_monitor(struct work_struct *work) // be that the work is in the pending state when // channels have been detached following by each // other. - queue_rcu_work(system_wq, &krwp->rcu_work); + queue_rcu_work(system_unbound_wq, &krwp->rcu_work); } } @@ -3704,7 +3704,7 @@ run_page_cache_worker(struct kfree_rcu_cpu *krcp) if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING && !atomic_xchg(&krcp->work_in_progress, 1)) { if (atomic_read(&krcp->backoff_page_cache_fill)) { - queue_delayed_work(system_wq, + queue_delayed_work(system_unbound_wq, &krcp->page_cache_work, msecs_to_jiffies(rcu_delay_page_cache_fill_msec)); } else { |